Defence lawyer Sam Norton said Ludowyke was involved in an earlier physical altercation at a nearby dog park and believed his victim knew the other man and could help identity him once she was "arrested".

She did not know either man.

During the attempted citizen's arrest, the nurse suffered a broken nose, two black eyes and scratches to her face, along with cuts and bruises.

The beating only stopped when a young couple came across the attack and pulled Ludowyke from his victim.

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Mr Norton said his client was "truly sorry" and described it as a "most unusual case".

He said Ludowyke suffered from a combination of anxiety disorders and had been treated for mental health issues since childhood.

Mr Norton asked magistrate Mary-Anne MacCallum to sentence him to a community corrections order, saying any jail time would cause him extreme anxiety and be greater punishment than for a person without his conditions.

Ludowyke, 50, who still lives with his parents, handed himself in to police 12 days after the attack.

"I was going to make a citizen's arrest, to make her tell me who he was," Ludowyke explained, in a police interview.

In an apology letter to his victims, Ludowyke said he felt "ashamed" of the attack, which had "shaken me to my core".

Police prosecutor Leading Senior Constable Les Hare said the attack was serious and deserved immediate jail.

"We've heard the accused has moved on, established a relationship and while that is positive for him, the victims in this case continue to suffer," he said.

Ludowyke, who also pleaded guilty to intentionally causing injury, affray and kicking a Siberian husky dog, had his bail extended until he is sentenced on December 6.